Self distracting pedicle screw distraction device

ABSTRACT

A pedicle screw distraction device that includes first and second pedicle screws each including a screw body portion and a ball head. The device also includes first and second screw head portions each including an internal threaded bore where the first screw is inserted in the first screw head portion and the second screw is inserted in the second screw head portion. The device also includes a connector link coupled to the first and second screw head portions where the connector link includes an outer perimeter portion having a slot therein. A spring member is positioned within the connector link between and in contact with the first and second screw head portions. A locking member including a plate and a separating portion is positioned between the screw head portions and an inside wall of the connector link where the separating portion is positioned between the screw head portions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 12/492,909, filed Jun. 26, 2009, titled “VertebralDisc Tensioning Device,” which is a continuation-in-part application ofU.S. patent application Ser. No. 11/646,750, filed Dec. 28, 2006, titled“Vertebral Disc Annular Fibrosis Tensioning and Lengthening Device,” nowU.S. Pat. No. 7,666,211, issued Feb. 23, 2010.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a pedicle screw distraction devicethat causes distraction between opposing vertebrae and, moreparticularly, to a pedicle screw distraction device that causesdistraction between opposing vertebrae, where the device includes aconnector link having a locking plate for locking pedicle screw heads tothe link and an angled end that provides a desired angle between thepedicle screws.

2. Discussion of the Related Art

The human spine includes a series of vertebrae interconnected byconnective tissue referred to as intervertebral discs that act as acushion between the vertebrae. The discs allow for movement of thevertebrae so that the spine can bend and rotate.

The intervertebral disc is an active organ in which the normal andpathologic anatomies are well known, but the normal and pathologicphysiologies have not been greatly understood. The intervertebral discpermits rhythmic motions required of all vertebrate animals in theirvarious forms of locomotion. The disc is a high-pressure system composedprimarily of absorbed water, an outer multilayered circumferentialannulus of strong, flexible, but essentially inelastic collagen fibers,and an inner core of a hydrogel called the nucleus pulposus. Theswelling of the contained hydrogel creates the high pressure thattightens the annular fibers and its laminations. Degeneration of discsin humans is typically a slow, complex process involving essentially allof the mechanical and physiologic components with loss of water holdingcapacity of the disc. Discogenic pain arises from either component, butis primarily due to altered chemistry. When this pain is severelydisabling and refractory to non-operative, the preferred contemporarytreatments are primarily surgical, particularly fusion and/or discreplacement.

Annular collagen fibers are arranged in circumferential belts orlaminations inserting strongly and tangentially in right- andleft-handed angulated patches into each adjacent vertebral body. Insidethe annular ring is contained an aggrecan, glycosaminoglycan, aprotein-sugar complex gel having great hygroscopic ability to holdwater. The swelling pressure of this gel of the nucleus maintains thepressure within the annulus, forcing the vertebrae apart and tighteningthe annular fibers. This tightening provides the primary mechanicalstability and flexibility of each disc of the spinal column. Further,the angulated arrangement of the fibers also controls the segmentalstability and flexibility of the motion segment. Therefore, the motionof each segment relates directly to the swelling capacity of the gel andsecondarily to the tightness of intact annulus fibers. The same gel isalso found in thin layers separating the annular laminar construction,providing some apparent elasticity and separating the laminations,reducing interlaminar torsional abrasion. With aging or degeneration,nucleus gel declines by desiccation or the loss of water, while collagencontent, including fibrosis, relatively increases.

Disc degeneration, which involves matrix, collagen and aggrecan, usuallybegins with annular tears or alterations in the endplate nutritionalpathways by mechanical or patho-physiological means. However, the discultimately fails for cellular reasons. As a person ages, the discs inthe spine go through a degenerative process that involves the gradualloss of the water holding capacity of the disc, referred to asdesiccation. As a result of this loss of water, the disc space heightmay partially or completely collapse, which may lead to chronic backpain disorders and/or leg pain as a result of the nerves being pinched.

Progressive injury and aging of the disc occurs normally in later lifeand abnormally after trauma or metabolic changes. In addition to thechemical effects on the free nerve endings as a source of discogenicpain, other degenerative factors may occur. Free nerve endings in theannular fibers may be stimulated or irritated by stretching as the discdegenerates, bulges, and circumferential delamination of annular fibersoccurs. This condition may lead to a number of problems. It has beenshown that a person's disc is typically taller in the morning when aperson awakes. This phenomenon may be due in part to the reduction ofbody weight forces on the disc when lying in a recumbent positionovernight that causes the disc height to restore and providerehydration. Therefore, the reduction of compressive forces on the discmay help to restore disc height and function.

As discussed above, as a person ages, the discs of the spine degenerate,and the disc space height collapses. Further, the ligaments and facetsof the spine degenerate as well due to increased forces and stresses onthese structures that occur as the disc loses its weight-bearingcapacity. These problems can lead to a reduction in the foraminal heightof the vertebrae. The neuro-foramen is an opening through the vertebraethat allows the nerve root of the spine to pass through. Because thenerve passes through the foramen, the nerve will often get pinched asthe disc height collapses, leading to various types of back pain.Further, these problems often lead to difficulty in walking.Additionally, lateral and central canal stenosis can occur as a resultof disc degeneration and collapse further causing the nerve roots to getpinched in the spinal canal. These conditions can lead to a conditionreferred to neurogenic claudication, where a patient can only walk ashort distance before experiencing considerable back and leg pain.Typically, patients respond by sitting down and bending forwardresulting in flexing of the spine and reducing pressure on the nervesrelieving their symptoms.

The treatment of degenerative disc disease and associated spine ailmentsis one of the most costly medical conditions with an estimated annualdirect cost in the United States of thirty-three billion dollars and atotal annual societal cost exceeding one hundred billion dollars.Indeed, in one's lifetime most individuals will experience an episode ofsignificant back and/or neck pain.

SUMMARY OF THE INVENTION

In accordance with the teachings of the present invention, a pediclescrew distraction device is disclosed that restores the loss of discheight as a result of disc degeneration and other factors. In oneembodiment, the device includes first and second pedicle screws eachincluding a screw body portion and a ball head. The device also includesfirst and second screw head portions each including an internal threadedbore where the first screw is inserted in the first screw head portionand the second screw is inserted in the second screw head portion. Thedevice also includes a connector link coupled to the first and secondscrew head portions where the connector link includes an outer perimeterportion having a slot therein. A spring member is positioned within theconnector link between and in contact with the first and second screwhead portions. A locking member including a plate and a separatingportion is positioned between the screw head portions and an inside wallof the connector link where the separating portion is positioned betweenthe screw head portions. The first screw head portion is rigidly coupledto the link and the second screw head portion is slidably coupled to thelink, and is able to move under the bias of the spring. The connectorlink includes an angled end that provides an angle between the pediclescrews.

Additional features of the present invention will become apparent fromthe following description and appended claims, taken in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a pedicle screw employed in a vertebraldisc annular fibrosis tensioning and lengthening device;

FIG. 2 is a perspective view of a spring employed in the vertebral discannular fibrosis tensioning and lengthening device;

FIG. 3 is a side view of the vertebral disc annular fibrosis tensioningand lengthening device of the invention including two of the pediclescrews with the spring therebetween;

FIG. 4 is a cross-sectional side view of the vertebral disc annularfibrosis tensioning and lengthening device shown in FIG. 3;

FIG. 5 is a top view of the vertebral disc annular fibrosis tensioningand lengthening device shown in FIG. 3;

FIG. 6 is a perspective view of a vertebral disc annular fibrosistensioning and lengthening device, according to another embodiment;

FIG. 7 is a side view showing a vertebral disc annular fibrosistensioning and lengthening device of the invention inserted withinadjacent vertebrae;

FIG. 8 is a top view of two vertebral disc annular fibrosis tensioningand lengthening devices of the invention inserted within the adjacentvertebrae;

FIG. 9 is a perspective view of a vertebral disc annular fibrosistensioning and lengthening device, according to another embodiment;

FIG. 10 is a cross-sectional view of the vertebral disc annular fibrosistensioning and lengthening device shown in FIG. 9;

FIG. 11 is a perspective view of a plate member used in the device shownin FIGS. 9 and 10;

FIG. 12 is a perspective view of a spring element used in the deviceshown in FIGS. 9 and 10;

FIG. 13 is a perspective view of a vertebral disc annular fibrosistensioning and lengthening device, according to another embodiment;

FIG. 14 is a broken-away, perspective view of a vertebral disc annularfibrosis tensioning and lengthening device, according to anotherembodiment;

FIG. 15 is a perspective view of a disc height restoration assembly;

FIG. 16 is a side view of a vertebral disc tensioning device, accordingto another embodiment;

FIG. 17 is a top view of the device shown in FIG. 16;

FIG. 18 is an exploded perspective view of the device shown in FIG. 16;

FIG. 19 is a cross-sectional view of the device shown in FIG. 16;

FIG. 20 is a perspective view of a pedicle screw and screw head portionin the device shown in FIG. 16;

FIG. 21 is a connector in the device shown in FIG. 16;

FIG. 22 is a bolt in the device shown in FIG. 16;

FIG. 23 is a spring assembly in the device shown in FIG. 16;

FIG. 24 is a side view of the device shown in FIG. 16 with the springhead portion pivoted relative to the connector;

FIG. 25 is a cross-sectional view of the illustration shown in FIG. 24;

FIG. 26 is a side view of a pedicle screw distraction assembly;

FIG. 27 is a top view of the assembly shown in FIG. 26;

FIG. 28 is a cross-sectional view of the assembly shown in FIG. 26;

FIG. 29 is an exploded perspective view of the assembly shown in FIG.26;

FIG. 30 is a perspective view of a pedicle screw and screw head portionseparated from the assembly shown in FIG. 26;

FIG. 31 is a perspective view of a screw link separated from theassembly shown in FIG. 26;

FIG. 32 is a perspective view of a locking member separated from theassembly shown in FIG. 26;

FIG. 33 is a side view of the locking member shown in FIG. 32 with aspring positioned therein;

FIG. 34 is a cross-sectional, perspective view of a portion of theassembly shown in FIG. 26 with a screw head portion in an insertionposition;

FIG. 35 is a cross-sectional, perspective view of the portion of theassembly shown in FIG. 34 with the screw head portion in a workingposition;

FIG. 36 is a cross-sectional, perspective view of the assembly shown inFIG. 26 with the locking member holding the screw head portions in theworking position; and

FIG. 37 is a perspective view of one of the screw head portionsseparated from the assembly shown in FIG. 26.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following discussion of the embodiments of the invention directed toa self distracting pedicle screw distraction device is merely exemplaryin nature, and is in no way intended to limit the invention or itsapplications or uses.

FIG. 1 is a perspective view of a pedicle screw 10 for use in avertebral disc annular fibrosis tensioning and lengthening device (FIG.3). The pedicle screw 10 includes a threaded and tapered body portion 12having a tip 14. The body portion 12 includes a plurality of holes 24that allow bone to grow therein when the screw 10 is threaded into thevertebral body so that the pedicle screw 10 is better anchored withinthe vertebra. The use of holes in the body portion of a pedicle screw tofacilitate bone growth therein can be employed in other types of pediclescrews for other uses besides vertebral disc annular fibrosis tensioningand lengthening devices, such as spinal fusion pedicle screw and rodinstrumentation, well known to those skilled in the art. The holes 24can come in a variety of numbers, diameters and configurations. In onenon-limiting embodiment, the diameter of the body portion 12 is about 8mm and the diameter of the holes is about 1.0 mm. The pedicle screw 10can include a bore 26 that extends through the body portion 12 to makeit cannulated so that a K-wire (not shown) can extend therethrough toallow for percutaneous placement of the pedicle screw over a K-wire thathas previously been placed through the vertebral pedicle. This willallow for a minimally invasive application of the device that causesless disruption of the normal anatomical structures of the spine andimproved recovery, as is well understood to those skilled in the art.

The pedicle screw 10 further includes a screw head 16 having an extendedcup shape defining a cavity 18. The cavity 18 includes an open side 20that fits a spring head (discussed below) and allows for mobilitybetween the spring head and the cavity 18 of the screw head 16. Thiswill permit mobility and will not limit flexion, extension and/orrotational mobility of the spine, thus allowing for the creation of aposterior motion-preserving device for reasons that will become apparentfrom the discussion below. An annular recess 22 is formed around anoutside of the head 16 also for reasons that will become apparent fromthe discussion below. The pedicle screw 10 can be made of any suitablematerial, such as titanium, stainless steel, etc., as would be wellunderstood to those skilled in the art. The cavity 18 could be made ofceramics or cobalt steel or cobalt chrome to limit wear between thespring head and the cavity 18.

FIG. 2 is a perspective view of a spring 30 having a cylindrical body 32that is also part of the vertebral disc annular fibrosis tensioning andlengthening device. A series of slots 34 are cut into the body portion32, as shown, in an alternating configuration that allows the bodyportion 32 to be compressed and provide an expansive spring force. Thespring 30 includes generally rounded ends 36 and 38 that are shaped toconform to the shape of the inner surface of the cavity 18. The spring30 can be made of any suitable material for the purposes describedherein, such as nitinol, which is a flexible metal having a memory.Other materials may also be suitable, such as a shape memory alloy,polymers, hydrogels, etc., which could expand over time and allow forseparation of the screw heads and disc height restoration. An example ofa suitable alloy includes about 50% nickel and about 50% titanium.

FIG. 3 is a side view, FIG. 4 is a cross-sectional view, side view andFIG. 5 is a top view of a vertebral disc annular fibrosis tensioning andlengthening device 40, according to an embodiment. The vertebral discannular fibrosis tensioning and lengthening device 40 includes two ofthe pedicle screws 10 where the open sides 20 of the heads 16 face eachother, as shown. The spring 30 is inserted into the cavities 18 of theheads 16 so that the ends 36 and 38 conform to the inner surface of thecavities 18. The inner surface of the cavities 18 and the ends 36 and 38can be coated with a suitable low friction material, such as chrome,cobalt, ceramic, etc., to prevent or reduce wear particle formation asthe spring 30 and the pedicle screws 10 rub against each other.Initially, the spring 32 is compressed so that it provides an expansiveforce to separate the pedicle screws 10. In one non-limiting embodiment,the expanded or relaxed length of the spring 30 is in the range of about3 cm-4 cm, which is about the height of a normal lumbar disc. Thediameter of the spring 32 can be any diameter suitable for the purposesdescribed herein.

An oval posterior ring 42 is positioned within the recesses 22, andoperates to maintain the screws 10 in their proper orientation, andprevent the pedicle screws 10 from separating beyond a predeterminedlimit. The fixed diameter of the ring 42 allows for the tips 14 of thepedicle screws 10 to separate greater relative to the heads 16. Thisimparts lordosis. Further, as the spring 30 causes the pedicle screws 10to separate, the ring 42 maintains the top end of the pedicle screws 10stationary to create a pivot and restore the height of the disc andlordosis of the spine. Also, the configuration and orientation of thespring 30, the ring 42 and the screws 10 preserves the motion of thespine as the person performs normal physical movement in that it allowsfor continued flexion, extension, as well as axial rotation of thespine. The spring 30 operates as a compressible link and the posteriorring 42 operates as a rigid link.

FIG. 6 is a perspective view of a vertebral disc annular fibrosistensioning and lengthening device 50, according to another embodiment,where like elements to the vertebral disc annular fibrosis tensioningand lengthening device 40 are identified by the same reference numeral.In this embodiment, the heads 16 of the pedicle screws 10 include a slot52. The ring 42 is replaced with a dumbbell member 54 including acylindrical body portion 56 and end portions 58 and 60. The body portion56 extends through the slots 52 so that the end portions 58 and 60 arepositioned on outside sides of the heads 16, and also operates to limitthe expansion of the pedicle screws 10 and control the posterior aspectsof the screws 10 and control the posterior aspects of the screws 10,thus allowing restoration of the lordosis, i.e., normal curvature, ofthe spine.

FIG. 7 is a side view and FIG. 8 is a top view of two of the vertebraldisc annular fibrosis tensioning and lengthening devices 40 coupled totwo adjacent lumbar vertebra 70 and 72 having a disc 68 therebetween.The pedicle screws 10 are threaded through pedicles 74 of the vertebra70 and 72 and into the vertebral body 76. Once the pedicle screws 10 arein place, then the spring 30 is positioned within the cavities 18 undercompression, as discussed above. As the spring bias forces the vertebra70 and 72 apart, the height of a disc space 78 between the vertebra 70and 72 increases and is restored. Further, as the height of the discspace 78 increases, the disc 68 is able to regenerate due to reducedsheer or compressive forces applied to the disc 68. The device 40creates a controlled distraction force and distraction distance on theannulus fibrosis and a controlled dynamic motion of the vertebra.Further, the device 40 allows motion of the spine while maintaining thestress tension effect on the disc 68. Particularly, the device 40provides a tension force across a compromised vertebral disc providing adistractive force to elicit the stress tension effect on the annulusfibrosis. The pedicle screws and links therebetween are arranged in aparallelogram shape to provide the desired distraction. Because mostsystems work like a hinge, the front or anterior portion of the discmoves much more than the back or posterior portion of the disc. This isnot a natural motion, so with the vertebral linkage of the invention, aparallel or near parallel motion of the disc can be achieved. In onenon-limiting embodiment, the motion pathway is an arc of a radius muchlonger than the pedicle screw length. Although the device 40 is showncoupled to adjacent vertebra, the device 40 can extend across anysuitable number of vertebrae to increase the disc space of more than onedisc.

The device 40 can also be applied unilaterally to restore coronalalignment. This is particularly applicable to patients suffering fromscoliosis where the curvature of the spine could be corrected byapplying the device 40 to the concaved portion of the spine. Restorationof spinal alignment would ultimately open the neural foramina on theconcaved side and help to alleviate symptoms of lower back painexperience by these patients.

Any suitable surgical procedure for placing the pedicle screws 10 can beused, including minimally invasive surgical procedures by making thepedicle screws 10 cannulated. In one known process of percutaneouspedicle screw instrumentation, a Jamshidi needle is used to dock on tothe junction of the vertebrae between the facet complex and thetransverse process of the vertebra. Gentle taps with a mallet cause theJamshidi needle to be advanced through the pedicle 74, making sure notto cross the medial border of the pedicle 74, which can result in nerveroot injury, until the junction between the pedicle base and thevertebral body is reached. Fluoroscopic visualization into the anteriorposterior and lateral planes of the vertebra is used to see theorientation of the Jamshidi needle. The correct trajectory of theJamshidi needle should place the tip of the needle in the center of thepedicle in the anterior posterior view when the tip of the Jamshidineedle lies at the pedicle vertebral body junction in the lateral view.

Once the junction between the base of the pedicle wall and the vertebralbody is reached, the Jamshidi needle can be directed in a more medialfashion. The Jamshidi needle is typically passed to about one-half thedepth of the vertebral body, and then a K-wire is passed down theJamshidi needle and into the vertebral body a little farther to seat itinto the bone. The Jamshidi needle is then removed. A series ofcannulated muscle dilators are then passed over the K-wire to preventthe soft tissue from going into the threads of the tap. The pedicle istapped and a cannulated pedicle screw is then passed down the dilators.

Although a specific type of spring has been described above for thevertebral disc annular fibrosis tensioning and lengthening device, thepresent invention contemplates any suitable linearly expandable linksuitable for the purposes described herein. The link exerts a forcecreating a stress tension effect within the disc allowing it toregenerate according to Wolff's law. The link also allows paralleldistraction of the disc, distraction along the coronal plane of the disctissue, and puts the annulus fibrous in tension and provides torsionalrotation of the vertebral construct. Further, the pedicle screws can bereplaced with any suitable mounting member. By a more generaldescription, the vertebral disc annular fibrosis tensioning andlengthening device includes a caudle vertebral body attachment memberand a cephelad vertebral body attachment member having a non-rigidinterconnection member therebetween that creates the tension stresseffect on the annulus fibrosis. The posterior ring 42 acts as a rigidmember coupled between the attachment members that also operates toprovide the distractive force.

FIG. 9 is a perspective view and FIG. 10 is a cross-sectional view of avertebral disc annular fibrosis tensioning and lengthening device 80,according to another embodiment, that illustrate other designs thatprovide the annular fibrosis tensioning and lengthening and restore thenatural lordosis of the spine in the manner discussed above. The device80 includes a pair of pedicle screws 82 each including a body portion 84having a ball head 86. The pedicle screw 82 also includes a pediclescrew head portion 88 having an internal threaded bore 90 through whichthe body portion 84 extends so that the ball head 86 is mounted on ashoulder 92 within the bore 90, as shown. A collar 94 is threaded intothe internal bore 90 of the pedicle screw head portion 88 and engages aslot 96 in the ball head 86 to rigidly hold the body portion 84 in placeat a proper kyphotic angle. The body portion 84 includes an internalbore 98 that accepts the Jamshidi needle for the reasons discussedabove.

When the pedicle screws 82 are properly placed in the vertebrae duringthe surgical procedure, a plate connector 100, shown separated from thedevice 80 in FIG. 11, is positioned over the pedicle screw head portions88 so that holes 102 and 104 in ends 108 and 110, respectively, in theplate connector 100 line up with the bores 90 in the pedicle screw headportions 88. Bolts 106 are then placed through the holes 102 and 104 andthreaded into the threaded bores 90 in the pedicle screw head portions88 to secure the plate connector 100 to the pedicle screws 82. The plateconnector 100 has a gradual U-shape, as shown, where the ends 108 and110 are slightly angled upward to provide the proper orientation for thedevice 80 that sets the maximum distraction of the disc.

In order to provide the distraction, a U-shaped spring element 112,shown separated from the device 80 in FIG. 12, is inserted between thepedicle screw head portions 88, where legs 114 and 116 of the springelement 112 push against the head portions 88, which cause the pediclescrew body portions 84 to pivot away from each other and cause the discheight to be restored in a lordotic manner. As the spring element 112separates the pedicle screws 82 to provide the distraction, the pediclescrew head portions 88 pivot on the plate 100 to provide the desireddistraction. Thus, the combination of the plate 100 and the springelement 112 provide the expandable and rigid link that operates in themanner as discussed above.

FIG. 13 is a perspective view of a vertebral disc annular fibrosistensioning and lengthening device 120, according to another embodiment,where like elements to the device 80 are identified by the samereference numeral. In the device 120, the spring 112 and the plate 100are combined or integrated into a single integrated element 122. Theplate part of the integrated element 122 is flat in this embodiment andincludes end pieces 124 and 126 through which the bolts 106 are placed.The element 122 includes limit stops 128 and 130 that limit the amountof distraction of the disc and also prevent overloading during jumpingand other high loading states. The spring part of the integrated element122 includes a live spring element 132 that provide the discdistraction. In this embodiment, an increased spring effect is providedby a spring loop portion 134 that extends the length of the springelement 132 to increase the distractive force.

The device 120 also includes an optional wedge member 136 positionedbetween one of the screw head portions 88 and the integrated element122, as shown. The wedge 136 is placed by the surgeon to provide changesin both height and angulations simultaneously, if desirable.

FIG. 14 is a perspective view of a vertebral annular fibrosis tensioningand lengthening device 150, according to another embodiment, where likeelements to the devices 80 and 120 are identified by the same referencenumeral. In this embodiment, the screw head portion 88 is replaced witha rounded screw head portion 152. The screw head portion 152 includes acylindrical cap portion 154 having an internal threaded bore 156. Aplate 158 is mounted to the cap portions 154 so that holes 160 and 162in the plate 158 line up with the bores 156. Bolts 164 are threaded intothe bores 156 to secure the plate 158 to the screws 82. A cylindricalspring element 168 having spaced apart slots 170 is positioned betweenthe rounded screw head portions 152, as shown, where the spring element168 is held in place by the relative shape between the ends of thespring element 168 and the head portions 152. The spring element 168provides the distractive force and the plate 158 provides the pivotlimiting force as described above.

FIG. 15 is a perspective view of a disc height restoration assembly 180including a plurality of pedicle screws 182 each including a bodyportion 184 and a head portion 186. The head portion 186 includes anopen U-shaped channel 188 defining opposing side walls 190 and 192 thatallow adjacent pedicle screws 182 to be positioned together, as shown. Aclip member 194 is positioned over adjacent side walls 192 of adjacentpedicle screws 182 to clip the adjacent pedicle screws 182 together andprovide a distracted force to the disc when the pedicle screws 182 aremounted to adjacent vertebrate. A spring element 196 is included.

FIG. 16 is a side view, FIG. 17 is a top view, FIG. 18 is a blown-apartperspective view and FIG. 19 is a cross-sectional perspective view of avertebral disc annular fibrosis tensioning and lengthening device 200,according to another embodiment. The device 200 is operable to providethe disc tensioning and lengthening as discussed above to restore thenatural lordosis of the spine. The device 200 includes a pair of pediclescrews 202 each having a body portion 204 and a ball head 206. Aninternal bore 208 extends through the body portion 206 and the ball head206 to accept a K-wire as discussed above. The device 200 also includesa screw head portion 210 having an internal threaded bore 212. FIG. 20is a perspective view of one of the pedicle screws 202 and one of thescrew head portions 210 separated from the device 200. The body portion204 of the screw 202 is inserted through a top end of the internal bore212 until the ball head 206 rests against a narrowed shoulder 214 in thehead portion 210 that allows the pedicle screw 202 to be pivotedrelative to the screw head portion 210, as discussed above. The screwhead portion 210 further includes a lateral cavity 216 that accepts aspring, as will be discussed in detail below. The screw head portion 210also includes a concave shaped top surface 218 also provided for reasonsthat will become apparent for discussion below.

The vertebral disc annular fibrosis tensioning and lengthening device200 also includes a screw connector 220 shown separated from the device200 in FIG. 21. The connector 220 includes a top plate 222 and opposingside plates 224 and 226, as shown. A support member 228 is connected tothe opposing side plates 224 and 226 opposite to the top plate 222. Inother words, the plates 224 and 226 are interconnected with a cross-linkfrom a construct on one side of the spinal cord to the other. Theconnector 220 includes a first opening 230 provided in a convex shapedportion 232 at one end of the top plate 222 and a second opening 234provided in a convex shaped portion 236 at an opposite end of the topplate 222 for reasons that will become apparent from the discussionbelow. The top plate 222 also includes a slot 240 through which a wedge238 is inserted into the device 200 to adjust a spring travel, as willalso be discussed below.

The device 200 also includes a pair of bolts 260, where one of the bolts260 is shown separated from the device 200 in FIG. 22. The bolt 260includes a bolt body 262 and a bolt head 264. An internal bore 266extends through the bolt 260 and aligns with the bore 208 in the pediclescrew 202. A half-mooned shaped collar 268 including an openingextending therethrough is positioned around the bolt body 262 just belowthe bolt head 264 of the bolt 260, as shown.

The device 200 also includes a spring assembly 270 shown separated fromthe device 200 in FIG. 23. The spring assembly 270 includes a baseportion 272 having a bore 274 therein. The spring assembly 270 alsoincludes a plunger 276 having a cylindrical body portion 280 and a headportion 278. A compressible spring member 282 including an internal bore284 is provided between the head portion 278 and the base portion 272where the body portion 280 extends through the bore 284 and into thebore 274, as shown. A compression force between the plunger 276 and thebase portion 272 causes the head portion 278 to push against the springmember 282 so that the body portion 280 extends farther into the channel274.

The device 200 is assembled so that the pedicle screws 202 are pivotallymounted within the screw head portions 210 and the spring member 282 ispositioned within the opposing cavities 216 of the head portions 210 sothat the head portion 278 of the plunger 276 is in one of the cavities216 and the base portion 272 is in the other cavity 216 of the otherscrew head portion 210. The connector 220 is then positioned over thescrew head portions 210 so that the side plates 224 and 226 are providedat sides of the screw head portions 210 and the top plate 222 covers thecavities 216 to hold the spring assembly 270 within the device 200. Inthis configuration, the shape of the concave shaped portions 232 and 236conforms to the concave surfaces 218 of the screw head portions 210. Thebolts 260 are then threaded into the threaded openings 212 through theopenings 230 and 234 to hold the connector 220 to the screw headportions 210. A bottom end of the bolts 260 is rounded to conform withthe shape of the ball heads 206. Thus, the ball heads 206 can rotatewithin the screw head portions 210 on the shoulders 214. When the bolts260 are threaded into the openings 212, the half-moon portions 268conform to an upper surface of the concave portions 232 and 236. Thus,the connector 220 provides the non-compressible link and the springassembly 270 provides the compressible link as discussed above toprovide the disc distraction and regeneration. The wedge 238 can bedriven through the hole 240 to conform with the head portion 278 of theplunger 276 to reduce the travel of the spring 282 if desired.

In addition to the pedicle screw 202 being able to pivot relative to thescrew head portion 210, the assembly of the pedicle screw 202, the screwhead portion 210 and the bolt 260 can pivot relative to the connector220. FIG. 25 is a cross-sectional view of the device 200 with the springassembly 270 removed and FIG. 24 is a side view of the device 200showing this feature. As is apparent, the orientation and shaping of theconcave surfaces 218 on the screw head portion 210, the concave shapedportions 232 and 236 of the plate connector and the half-moon shape ofthe collars 268 allow the spring head portions 210 and the collars 268to pivot relative to the connector 222 when the bolt 260 is threadedinto the threaded bore 212.

FIG. 26 is a side view, FIG. 27 is a top view, FIG. 28 is across-sectional view and FIG. 29 is a blown-apart, perspective view of aself distracting pedicle screw distraction device assembly 300 that isoperable to provide the disc tensioning and lengthening as discussedabove to restore disc height and the natural lordosis of the spine. Thedevice assembly 300 includes a pair of pedicle screws 302 each having abody portion 304 and a ball head 306. An internal bore 308 extendsthrough the body portion 304 and the ball head 306 to accept a K-wire,as discussed above. The device assembly 300 also includes a pair ofscrew head portions 310 each having an internal threaded bore 312. FIG.30 is a perspective view of one of the pedicle screws 302 and associatedscrew head portion 310 separated from the device assembly 300. The bodyportion 304 of the screw 302 is inserted through a top end of theinternal bore 312 until the ball head 306 rests against a shoulder 314at a bottom end of the head portion 310 that allows the pedicle screw302 to be pivoted relative to the screw head portion 310. A threaded setscrew 316 is threaded into the threaded bore 312 of the head portion 310by inserting a wrench (not shown) into an opening 318 in the set screw316 to lock the pedicle screw 302 at a specific angle relative to thehead portion 310 against the shoulder 314.

A cylindrical protrusion 322 extends from an outside surface of the headportion 310 for reasons that will become apparent from the discussionbelow. Further, a bottom edge flange 324 is provided on one side of thehead portion 310 and opposing top and bottom edge flanges 326 and 328are provided at an opposite side of the head portion 310 to define aslot 330 therebetween, also for reasons that will become apparent fromthe discussion below.

The device assembly 300 also includes a screw link 340 shown separatedfrom the device assembly 300 in FIG. 31. The screw link 340 is anelongated oval sleeve member having an outer perimeter portion 342defining an internal slot 344. One end 346 of the link 340 is angled atlocation 348 relative to an opposite end 350 of the link 340 to providean angled orientation between the pedicle screws 302 and a lordoticseparation between the pedicle screws 302, as will be discussed in moredetail below. An angled edge 352 and a slot 354 are provided on aninside surface of a side rail 356 at a central internal location of theperimeter portion 342, and an angled edge 358 and a slot (not shown) areprovided on an inside surface of a side rail 360 of the perimeterportion 342 also for reasons that will become apparent from thediscussion below. An arced brace 362 connects the opposing side rails356 and 360 at a bottom location of the perimeter portion 342.

The device assembly 300 also includes an elongated locking member 370shown separated from the device assembly 300 in FIGS. 32 and 33. Thelocking member 370 includes a locking plate 372 having an angled end 374that conforms with the angled end 346 of the link 340. A separatingportion 376 extends perpendicular from the locking plate 372 andincludes a cylindrical opening 378 that conforms to and accepts a spring380. The separating portion 376 includes a flange 382 opposite to theplate 372 and a tab 384 adjacent to the flange 382, as shown.

The locking member 370 locks the screw head portions 310 to the link 340as shown in FIGS. 34, 35 and 36. During assembly, the screw head portion310 is inserted up through the slot 344 in the link 340 where the sideof the screw head portion 310 adjacent to the flange 324 rides along aninside surface of the rail 356 of the perimeter portion 342 until theflange 324 contacts a bottom surface of the rail 356. In this position,the opposing flanges 326 and 328 are provided above and below theopposite rail 360 of the perimeter portion 342 where the height of therail 360 matches the width of the slot 330. The screw head portion 310is then slid over so that the rail 360 slides into the slot 330 and theflanges 326 and 328 are positioned at top and bottom surfaces of therail 360, as shown in FIG. 35. In this configuration, the flange 324still contacts the bottom surface of the rail 356, but there is a gapbetween the outside surface of the screw head portion 310 and the rail356.

With the spring 380 positioned within the cylindrical opening 378, thelocking member 370 is inserted into the link 340 so that the plate 372is positioned within the gap between the screw head portions 310 and therail 356, and the separating portion 376 is positioned between the screwhead portions 310. The tab 384 rides along the edge 352 and is insertedinto the slot 354 on the rail 356 in a snap-fit engagement, and theopposing tab rides along the edge 358 and is inserted in the opposingslot in a snap-fit engagement to lock the locking member 370 to theconnector link 340 and hold the entire assembly 300 together. The spring380 is held in place within the opening 378 by the brace 362 where theprotrusions 322 are positioned within opposite ends of the spring 380.

The spring 380 is under compression so that it applies a separatingforce to the screw head portions 310. In one non-limiting embodiment,the spring 380 has a spring constant value in the range of 0-1000pounds/inch. The angle between the ends 346 and 350 of the link 340causes the screws 302 to be separated in a lordotic manner under thebias of the spring 380 as dictated by the angle between the ends 346 and350, where the angle can vary between 0° and 30°. The locking member 370is configured so that the separating portion 376 is offset relative tothe center of the plate 372, where one of the pedicle screws 302 andassociated screw head portion 310 are positioned in a short segmentbetween the separating portion 376 and the end 346 of the link 340 andthe other pedicle screw 302 and associated screw head portion 310 arepositioned in a long segment between the separating portion 376 and theend 350 of the link 340.

When the assembly 300 is being assembled during the surgical procedurein the manner as discussed above, the pedicle screw 302 and associatedscrew head portion 310 provided in the short segment is locked in placeby positioning a series of detents 384 within corresponding openings(not shown) in an underside of the rail 360 of the link 340. When thesurgeon is assembling the assembly 300 during the surgical procedure, hewill insert the screw head portion 310 in the short segment of the link340 in the desired positioned so that the detents 384 are positionedwithin the desired openings that allows an adjustment of the screw headportion 310 along the short segment. In one non-elimiting embodiment,the range of position of the screw head portion 310 is provided by fourof the detents 384 and is about 0-8 mm. This is by way of a non-limitingexample, where a different number of detents 384 possibly having adifferent spacing can provide other ranges. Once the locking member 370is in place, the screw head portion 310 having the detents 384 is heldin that position. The other screw 302 and screw head portion 310positioned within the long segment in the link 340 is free to slidealong the long segment. When the pedicle screws 302 are inserted intothe pedicle of the vertebra, and the spring 380 provides the separatingforce between the screw head portions 310, the disc is distracted by theability of the screw head portion 310 in the long segment to slide alongthe link 340, where the angle of the screws 302 as set by the set screws316 and the angle between the ends 346 and 350 of the link 340 providethe separation in line lordotic manner.

The foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. One skilled in the art willreadily recognize from such discussion and from the accompanyingdrawings and claims that various changes, modifications and variationscan be made therein without departing from the spirit and scope of theinvention as defined in the following claims.

What is claimed is:
 1. A distraction device comprising: first and secondscrews each including a ball head and a screw body; first and secondscrew head portions each including an internal threaded bore and ashoulder therein, said first screw being inserted into the internal boreof the first screw head portion so that the ball head of the first screwis positioned against the shoulder of the first screw head portion andsaid second screw being inserted into the internal bore of the secondscrew head portion so that the ball head of the second screw ispositioned against the shoulder of the second screw head portion; aconnector link coupled to the first and second screw head portions, saidconnector link including an outer perimeter portion having a slottherein; a spring member positioned within the connector link betweenand in contact with the first and second screw head portions; and alocking member including a plate and a separating portion, said platebeing positioned between the screw head portions and an inside wall ofthe connector link and the separating portion being positioned betweenthe screw head portions.
 2. The device according to claim 1 wherein theconnector link includes an angled end that provides an angle between thefirst and second screws.
 3. The device according to claim 1 wherein thespring member is positioned adjacent to the separating portion.
 4. Thedevice according to claim 1 wherein each of the first and second screwhead portions includes a pair of opposing flanges that couple the screwhead portion to a side rail of the perimeter portion of the connectorlink.
 5. The device according to claim 4 wherein the opposing flangesallow at least one of the screw head portions to slide along the siderail of the connector link.
 6. The device according to claim 5 whereinthe separating portion provides a short separating length in which thefirst screw head portion is positioned and a long separating lengthwhere the second screw head portion is positioned, wherein the secondscrew head portion is operable to slide along the side rail in the longseparating length.
 7. The device according to claim 6 wherein one of theflanges on the first screw head portion includes at least one detentthat is positioned within a corresponding opening in the side rail ofthe connector link to secure the first screw head portion to theconnector link at a fixed location.
 8. The device according to claim 7wherein the at least one detent is a plurality of detests that can beselectively positioned within a plurality of corresponding openings inthe side rail of the connector link so that the first screw head portionis operable to be positioned at different locations of the short length.9. The device according to claim 1 wherein the first and second screwsare first and second pedicle screws, and wherein the first screw headportion further includes a first set screw having an end that conformswith the ball head of the first pedicle screw, where the first set screwis threaded into the threaded bore to hold the first pedicle screwagainst the shoulder, and said second screw head portion furtherincluding a second set screw having an end that conforms with the ballhead of the second pedicle screw, where the second set screw is threadedinto threaded bore to hold the second pedicle screw against theshoulder.
 10. The device according to claim 1 wherein the first screwhead portion is rigidly mounted to the connector link and the secondscrew head portion is slidably mounted to the connector link.
 11. Adistraction device for distracting a vertebral disc, said devicecomprising: first and second pedicle screws each including a ball headand a screw body; first and second screw head portions each including aninternal threaded bore and a shoulder therein, said first pedicle screwbeing inserted into the internal bore of the first screw head portion sothat the ball head of the first pedicle screw is positioned against theshoulder of the first screw head portion and said second pedicle screwbeing inserted into the internal bore of the second screw head portionso that the ball head of the second screw is positioned against theshoulder of the second screw head portion, said first screw head portionfurther including a first set screw having an end that conforms with theball head of the first pedicle screw, where the first set screw isthreaded into the threaded bore to hold the first pedicle screw againstthe shoulder, said second screw head portion further including a secondset screw having an end that conforms with the ball head of the secondpedicle screw, where the second set screw is threaded into the threadedbore to hold the second pedicle screw against the shoulder, each of thefirst and second screw head portions further including opposing flangesdefining a slot therebetween; a connector link including an outerperimeter portion defining first and second opposing side rails eachdefining a slot therebetween and an angled end that provides an anglebetween the first and second pedicle screws, wherein the first side railis positioned in the slot between the opposing flanges of the firstscrew head portion and the second side rail is positioned within theslot between the opposing flanges of the second screw head portion; aspring member positioned within the connector link between and incontact with the first and second screw head portions; and a lockingmember including a plate and a separating portion, said plate beingpositioned between the first and second screw head portions and thesecond rail and the separating portion being positioned between thefirst and second screw head portions, wherein the first screw headportion is rigidly mounted to the connector link and the second screwhead portion is slidably mounted to the connector link under a bias ofthe spring so as to distract the disc.
 12. The device according to claim11 wherein the spring member is positioned adjacent to the separatingportion.
 13. The device according to claim 11 wherein the separatingportion provides a short separating length in which the first screw headportion is positioned and a long separating length where the secondscrew head portion is positioned, wherein the second screw head portionis operable to slide along the side rail in the long separating length.14. The device according to claim 13 wherein one of the flanges on thefirst screw head portion includes at least one detent that is positionedwithin a corresponding opening in the side rail of the connector link tosecure the first screw head portion to the connector link at a fixedlocation.
 15. The device according to claim 14 wherein the at least onedetent is a plurality of detents that can be selectively positionedwithin a plurality of corresponding openings in the side rail of theconnector link so that the first screw head portion is operable to bepositioned at different locations of the short length.
 16. A distractiondevice for distracting a vertebral disc, said device comprising a firstpedicle screw including a first screw head portion, a second pediclescrew including a second screw head portion, a connector link coupled tothe first and second screw head portions, said connector link includingan outer perimeter portion having a slot therein and a spring memberpositioned within the connector link between and in contact with thefirst and second screw head portions, wherein the first screw headportion is rigidly mounted to the connector link and the second screwhead portion is slidably mounted to the connector link under a bias ofthe spring so as to distract the disc.
 17. The device according to claim16 further comprising a locking member including a plate and aseparating portion, said plate being positioned between the first andsecond screw head portions and a side rail of the connector link and theseparating portion being positioned between the first and second screwhead portions.
 18. The device according to claim 17 wherein theseparating portion provides a short separating length in which the firstscrew head portion is positioned and a long separating length where thesecond screw head portion is positioned, wherein the second screw headportion is operable to slide along the side rail in the long separatinglength.
 19. The device according to claim 16 wherein each of the firstand second screw head portions includes a pair of opposing flanges thatcouple the screw head portion to a side rail of the perimeter portion ofthe connector link.
 20. The device according to claim 16 wherein theconnector link includes an angled end that provides an angle between thefirst and second screws.